The present invention relates to a positive resist composition suitable for use in the production, for example, of semiconductor integrated circuit elements, masks for producing integrated circuits, printed circuit boards and liquid crystal panels.
As positive resist compositions, chemically amplified resist composition as described, for example, in U.S. Pat. No. 4,491,628 and European Patent 249,139 are known. The chemically amplified positive resist composition is a pattern formation material which generates an acid in an exposed area upon irradiation of radiation, for example, a far ultraviolet ray and due to a reaction using the acid as a catalyst, solubility in a developing solution differentiates in the area irradiated with the active radiation from the non-irradiated area to form a pattern on a substrate.
In general, the chemically amplified positive resist composition is roughly divided into three types, i.e., a three-component type, a two-component type and a hybrid type. The resist composition of three-component type comprises an alkali-soluble resin, a compound (hereinafter referred to as a xe2x80x9cphoto-acid generatorxe2x80x9d sometimes) that generates an acid upon irradiation of radiation and a dissolution inhibiting compound having an acid-decomposable group to the alkali-soluble resin. The resist composition of two-component type comprises a resin having a group capable of being decomposed by a reaction with an acid to become alkali-soluble and a photo-acid generator. The resist composition of hybrid type comprises a resin having a group capable of being decomposed by a reaction with an acid to become alkali-soluble, a low molecular weight dissolution inhibiting compound having an acid-decomposable group and a photo-acid generator.
Various techniques for improving performances are known wherein two or more resins, which are decomposed by the action of an acid to increase solubility in an alkali developing solution (hereinafter referred to as xe2x80x9cacid-decomposable resinxe2x80x9d sometimes) are used in combination in the chemically amplified positive resist compositions.
However, these techniques still have a problem in a performance of a linewidth variation rate caused by fluctuation of thickness of a resist film on a highly reflective substrate having irregularities (for example, bare silicon substrate or polysilicon substrate).
Therefore, an object of the present invention is to provide a chemically amplified positive resist composition in which the linewidth variation rate is small and which exhibits good performances without real damage even when provided on the highly reflective substrate having irregularities.
Other objects of the present invention will become apparent from the following description.
As a result of the intensive investigations on the chemically amplified positive resist compositions, it has been found that the objects of the present invention are accomplished by the positive resist composition comprising two kinds of resins having acid-decomposable groups of specific structures to complete the present invention.
The positive resist composition of the present invention includes the following constructions.
(1) A positive resist composition comprising: (a) a resin (A), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (X) shown below and/or a resin (B), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Y) shown below, and a resin (C), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Q) shown below; and (b) a compound that generates an acid upon irradiation of an actinic ray or radiation. 
In formula (X), R1 and R2, which may be the same or different, each represent a hydrogen atom or an alkyl group which may have a substituent; m represents an integer of from 1 to 20; and Z1 represents 
In the formulae above, R3 represents an alkyl group which may have a substituent, an aryl group which may have a substituent or an aralkyl group which may have a substituent; and n represents an integer of from 0 to 5, 
In formula (Y), R4 represents an alkyl group, 
In formula (Q), R5 and R6, which may be the same or different, each represent a hydrogen atom or an alkyl group; X represents an alkylene group which may have a substituent; Y represents a divalent connecting group; Z2 represents a heterocyclic group which may have a substituent; and 1 represents 0 or 1.
(2) The positive resist composition as described in item (1) above, wherein the compound that generates an acid upon irradiation of an actinic ray or radiation of component (b) is a compound having a sulfonium salt structure or a compound having a diazodisulfone structure.
(3) The positive resist composition as described in item (1) above, wherein the compound that generates an acid upon irradiation of an actinic ray or radiation of component (b) is a combination of a compound having a sulfonium salt structure and a compound having a diazodisulfone structure.
The positive resist composition of the present invention will be described in more detail below.
(a-1) Resin (A), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (X) described above:
In formula (X), R1 and R2, which may be the same or different, each represent a hydrogen atom or an alkyl group which may have a substituent, and m represents an integer of from 1 to 20.
The alkyl group represented by R1 or R2 may be a straight chain, branched or cyclic alkyl group.
The straight chain alkyl group has preferably from 1 to 30 carbon atoms, more preferably from 1 to 20 carbon atoms, and includes, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl and n-decyl groups.
The branched alkyl group has preferably from 3 to 30 carbon atoms, more preferably from xe2x88x923 to 20 carbon atoms, and includes, for example, isopropyl, isobutyl, tert-butyl, isopentyl, tert-pentyl, isohexyl, tert-hexyl, isoheptyl, tert-heptyl, isooctyl, tert-octyl, isononyl and tert-decyl groups.
The cyclic alkyl group has preferably from 3 to 30 carbon atoms, more preferably from 3 to 20 carbon atoms, and includes, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl and cyclodecyl groups.
In the groups represented by Z1, R3 represents an alkyl group which may have a substituent, an aryl group which may have a substituent or an aralkyl group which may have a substituent. The alkyl group may be a straight chain, branched or cyclic alkyl group. n represents an integer of from 0 to 5.
The straight chain or branched alkyl group represented by R3 has preferably up to 30 carbon atoms, more preferably up to 20 carbon atoms, and includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, isohexyl, tert-hexyl, n-heptyl, isoheptyl, tert-heptyl, n-octyl, isooctyl, tert-octyl, n-nonyl, isononyl, tert-nonyl, n-decyl, isodecyl, tert-decyl, n-undecyl, isoundecyl, n-dodecyl, isododecyl, n-tridecyl, isotridecyl, n-tetradecyl, isotetradecyl, n-pentadecyl, isopentadecyl, n-hexadecyl, isohexadecyl, n-heptadecyl, isoheptadecyl, n-octadecyl, isooctadecyl, n-nonadecyl and isononadecyl groups.
The cyclic alkyl group represented by R3 has preferably from 3 to 30 carbon atoms, more preferably from 3 to 20 carbon atoms. The cyclic alkyl group may be a cycloalkyl group including a ring containing up to 20 carbon atoms or a cycloalkyl group having a substituent. The cyclic alkyl group includes, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl, cyclotridecyl, cyclotetradecyl, cyclopentadecyl, cyclohexadecyl, cycloheptadecyl, cyclooctadecyl, cyclononadecyl, 4-cyclohexylcyclohexyl, 4-n-hexylcyclohexyl, pentylcyclohexyl, hexyloxycyclohexyl and pentyloxycyclohexyl groups. Substituted cycloalkyl groups other than those described above may be used as long as they have carbon atoms within the above described range.
The aryl group represented by R3 has preferably from 6 to 30 carbon atoms, more preferably from 6 to 20 carbon atoms, and includes, for example, phenyl, 4-methylphenyl, 3-methylphenyl, 2-methylphenyl, 4-ethylphenyl, 3-ethylphenyl, 2-ethylphenyl, 4-n-propylphenyl, 3-n-propylphenyl, 2-n-propylphenyl, 4-isopropylphenyl, 3-isopropylphenyl, 2-isopropylphenyl, 4-cyclopropylphenyl, 3-cyclopropylphenyl, 2-cyclopropylphenyl, 4-n-butylphenyl, 3-n-butylphenyl, 2-n-butylphenyl, 4-isobutylphenyl, 3-isobutylphenyl, 2-isobutylphenyl, 4-tert-butylphenyl, 3-tert-butylphenyl, 2-tert-butylphenyl, 4-cyclobutylphenyl, 3-cyclobutylphenyl, 2-cyclobutylphenyl, 4-cyclopentylphenyl, 4-cyclohexylphenyl, 4-cyclohepylphenyl, 4-cyclooctylphenyl, 2-cyclopentylphenyl, 2-cyclohexylphenyl, 2-cyclohepylphenyl, 2-cyclooctylphenyl, 3-cyclopentylphenyl, 3-cyclohexylphenyl, 3-cyclohepylphenyl, 3-cyclooctylphenyl, 4-cyclopentyloxyphenyl, 4-cyclohexyloxyphenyl, 4-cyclohepyloxyphenyl, 4-cyclooctyloxyphenyl, 2-cyclopentyloxyphenyl, 2-cyclohexyloxyphenyl, 2-cyclohepyloxyphenyl, 2-cyclooctyloxyphenyl, 3-cyclopentyloxyphenyl, 3-cyclohexyloxyphenyl, 3-cyclohepyloxyphenyl, 3-cyclooctyloxyphenyl, 4-n-pentylphenyl, 4-n-hexylphenyl, 4-n-heptylphenyl, 4-n-octylphenyl, 2-n-pentylphenyl, 2-n-hexylphenyl, 2-n-heptylphenyl, 2-n-octylphenyl, 3-n-pentylphenyl, 3-n-hexylphenyl, 3-n-heptylphenyl, 3-n-octylphenyl, 2,6-diisopropylphenyl, 2,3-diisopropylphenyl, 2,4-diisopropylphenyl, 3,4-diisopropylphenyl, 2,6-di-tert-butylphenyl, 2,3-di-tert-butylphenyl, 2,4-di-tert-butylphenyl, 3,4-di-tert-butylphenyl, 2,6-di-n-butylphenyl, 2,3-di-n-butylphenyl, 2,4-di-n-butylphenyl, 3,4-di-n-butylphenyl, 2,6-diisobutylphenyl, 2,3-diisobutylphenyl, 2,4-diisobutylphenyl, 3,4-diisobutylphenyl, 2,6-di-tert-amylphenyl, 2,3-di-tert-amylphenyl, 2,4-di-tert-amylphenyl, 3,4-di-tert-amylphenyl, 2,6-diisoamylphenyl, 2,3-diisoamylphenyl, 2,4-diisoamylphenyl, 3,4-diisoamylphenyl, 2,6-di-n-pentylphenyl, 2,3-di-n-pentylphenyl, 2,4-di-n-pentylphenyl, 3,4-di-n-pentylphenyl, 4-adamantylphenyl, 2-adamantylphenyl, 4-isobornylphenyl, 3-isobornylphenyl, 2-isobornylphenyl, 4-cyclopentyloxyphenyl, 4-cyclohexyloxyphenyl, 4-cycloheptyloxyphenyl, 4-cyclooctyloxyphenyl, 2-cyclopentyloxyphenyl, 2-cyclohexyloxyphenyl, 2-cycloheptyloxyphenyl, 2-cyclooctyloxyphenyl, 3-cyclopentyloxyphenyl, 3-cyclohexyloxyphenyl, 3-cycloheptyloxyphenyl, 3-cyclooctyloxyphenyl, 4-n-pentyloxyphenyl, 4-n-hexyloxyphenyl, 4-n-heptyloxyphenyl, 4-n-octyloxyphenyl, 2-n-pentyloxyphenyl, 2-n-hexyloxyphenyl, 2-n-heptyloxyphenyl, 2-n-octyloxyphenyl, 3-n-pentyloxyphenyl, 3-n-hexyloxyphenyl, 3-n-heptyloxyphenyl, 3-n-octyloxyphenyl, 2,6-diisopropyloxyphenyl, 2,3-diisopropyloxyphenyl, 2,4-diisopropyloxyphenyl, 3,4-diisopropyloxyphenyl, 2,6-di-tert-butyloxyphenyl, 2,3-di-tert-butyloxyphenyl, 2,4-di-tert-butyloxyphenyl, 3,4-di-tert-butyloxyphenyl, 2,6-di-n-butyloxyphenyl, 2,3-di-n-butyloxyphenyl, 2,4-di-n-butyloxyphenyl, 3,4-di-n-butyloxyphenyl, 2,6-diisobutyloxyphenyl, 2,3-diisobutyloxyphenyl, 2,4-diisobutyloxyphenyl, 3,4-diisobutyloxyphenyl, 2,6-di-tert-amyloxyphenyl, 2,3-di-tert-amyloxyphenyl, 2,4-di-tert-amyloxyphenyl, 3,4-di-tert-amyloxyphenyl, 2,6-diisoamyloxyphenyl, 2,3-diisoamyloxyphenyl, 2,4-diisoamyloxyphenyl, 3,4-diisoamyloxyphenyl, 2,6-di-n-pentyloxyphenyl, 2,3-di-n-pentyloxyphenyl, 2,4-di-n-pentyloxyphenyl, 3,4-di-n-pentyloxyphenyl, 4-adamantyloxyphenyl, 3-adamantyloxyphenyl, 2-adamantyloxyphenyl, 4-isobornyloxyphenyl, 3-isobornyloxyphenyl and 2-isobornyloxyphenyl. These examples of the aryl group may further have substituents other than those described above as long as they have carbon atoms within the above described range.
The aralkyl group represented by R3 has preferably from 7 to 30 carbon atoms, more preferably from 7 to 20 carbon atoms, and includes, for example, phenylethyl, 4-methylphenylethyl, 3-methylphenylethyl, 2-methylphenylethyl, 4-ethylphenylethyl, 3-ethylphenylethyl, 2-ethylphenylethyl, 4-n-propylphenylethyl, 3-n-propylphenylethyl, 2-n-propylphenylethyl, 4-isopropylphenylethyl, 3-isopropylphenylethyl, 2-isopropylphenylethyl, 4-cyclopropylphenylethyl, 3-cyclopropylphenylethyl, 2-cyclopropylphenylethyl, 4-n-butylphenylethyl, 3-n-butylphenylethyl, 2-n-butylphenylethyl, 4-isobutylphenylethyl, 3-isobutylphenylethyl, 2-isobutylphenylethyl, 4-tert-butylphenylethyl, 3-tert-butyiphenylethyl, 2-tert-butyiphenylethyl, 4-cyclobutylphenylethyl, 3-cyclobutylphenylethyl, 2-cyclobutylphenylethyl, 4-cyclopentylphenylethyl, 4-cyclohexylphenylethyl, 4-cyclohepylphenylethyl, 4-cyclooctylphenylethyl, 2-cyclopentylphenylethyl, 2-cyclohexylphenylethyl, 2-cyclohepylphenylethyl, 2-cyclooctylphenylethyl, 3-cyclopentylphenylethyl, 3-cyclohexylphenylethyl, 3-cyclohepylphenylethyl, 3-cyclooctylphenylethyl, 4-cyclopentyloxyphenylethyl, 4-cyclohexyloxyphenylethyl, 4-cyclohepyloxyphenylethyl, 4-cyclooctyloxyphenylethyl, 2-cyclopentyloxyphenyl, 2-cyclohexyloxyphenyl, 2-cyclohepyloxyphenylethyl, 2-cyclooctyloxyphenylethyl, 3-cyclopentyloxyphenylethyl, 3-cyclohexyloxyphenylethyl, 3-cyclohepyloxyphenylethyl, 3-cyclooctyloxyphenylethyl, 4-n-pentylphenylethyl, 4-n-hexylphenylethyl, 4-n-heptylphenylethyl, 4-n-octylphenylethyl, 2-n-pentylphenylethyl, 2-n-hexylphenylethyl, 2-n-heptylphenylethyl, 2-n-octylphenylethyl, 3-n-pentylphenylethyl, 3-n-hexylphenylethyl, 3-n-heptylphenylethyl, 3-n-octylphenylethyl, 2,6-diisopropylphenylethyl, 2,3-diisopropylphenylethyl, 2,4-diisopropylphenylethyl, 3,4-diisopropylphenylethyl, 2,6-di-tert-butylphenylethyl, 2,3-di-tert-butylphenylethyl, 2,4-di-tert-butylphenylethyl, 3,4-di-tert-butylphenylethyl, 2,6-di-n-butylphenylethyl, 2,3-di-n-butylphenylethyl, 2,4-di-n-butylphenylethyl, 3,4-di-n-butylphenylethyl, 2,6-diisobutylphenylethyl, 2,3-diisobutylphenylethyl, 2,4-diisobutylphenylethyl, 3,4-diisobutylphenylethyl, 2,6-di-tert-amylphenylethyl, 2,3-di-tert-amylphenylethyl, 2,4-di-tert-amylphenylethyl, 3,4-di-tert-amylphenylethyl, 2,6-diisoamylphenylethyl, 2,3-diisoamylphenylethyl, 2,4-diisoamylphenylethyl, 3,4-diisoamylphenylethyl, 2,6-di-n-pentylphenylethyl, 2,3-di-n-pentylphenylethyl, 2,4-di-n-pentylphenylethyl, 3,4-di-n-pentylphenylethyl, 4-adamantylphenylethyl, 3-adamantylphenylethyl, 2-adamantylphenylethyl, 4-isobornylphenylethyl, 3-isobornylphenylethyl, 2-isobornylphenylethyl, 4-cyclopentyloxyphenylethyl, 4-cyclohexyloxyphenylethyl, 4-cycloheptyloxyphenylethyl, 4-cyclooctyloxyphenylethyl, 2-cyclopentyloxyphenylethyl, 2-cyclohexyloxyphenylethyl, 2-cycloheptyloxyphenylethyl, 2-cyclooctyloxyphenylethyl, 3-cyclopentyloxyphenylethyl, 3-cyclohexyloxyphenylethyl, 3-cycloheptyloxyphenylethyl, 3-cyclooctyloxyphenylethyl, 4-n-pentyloxyphenylethyl, 4-n-hexyloxyphenylethyl, 4-n-heptyloxyphenylethyl, 4-n-octyloxyphenylethyl, 2-n-pentyloxyphenylethyl, 2-n-hexyloxyphenylethyl, 2-n-heptyloxyphenylethyl, 2-n-octyloxyphenylethyl, 3-n-pentyloxyphenylethyl, 3-n-hexyloxyphenylethyl, 3-n-heptyloxyphenylethyl, 3-n-octyloxyphenylethyl, 2,6-diisopropyloxyphenylethyl, 2,3-diisopropyloxyphenylethyl, 2,4-diisopropyloxyphenylethyl, 3,4-diisopropyloxyphenylethyl, 2,6-di-tert-butyloxyphenylethyl, 2,3-di-tert-butyloxyphenylethyl, 2,4-di-tert-butyloxyphenylethyl, 3,4-di-tert-butyloxyphenylethyl, 2,6-di-n-butyloxyphenylethyl, 2,3-di-n-butyloxyphenylethyl, 2,4-di-n-butyloxyphenylethyl, 3,4-di-n-butyloxyphenylethyl, 2,6-diisobutyloxyphenylethyl, 2,3-diisobutyloxyphenylethyl, 2,4-diisobutyloxyphenylethyl, 3,4-diisobutyloxyphenylethyl, 2,6-di-tert-amyloxyphenylethyl, 2,3-di-tert-amyloxyphenylethyl, 2,4-di-tert-amyloxyphenylethyl, 3,4-di-tert-amyloxyphenylethyl, 2,6-diisoamyloxyphenylethyl, 2,3-diisoamyloxyphenylethyl, 2,4-diisoamyloxyphenylethyl, 3,4-diisoamyloxyphenylethyl, 2,6-di-n-pentyloxyphenylethyl, 2,3-di-n-pentyloxyphenylethyl, 2,4-di-n-pentyloxyphenylethyl, 3,4-di-n-pentyloxyphenylethyl, 4-adamantyloxyphenylethyl, 3-adamantyloxyphenylethyl, 2-adamantyloxyphenylethyl, 4-isobornyloxyphenylethyl, 3-isobornyloxyphenylethyl and 2-isobornyloxyphenylethyl, and groups wherein the ethyl groups in the above specific examples of the aralkyl group are replaced by other alkyl groups, for example, methyl groups, propyl groups or butyl groups.
Examples of the substituent for the above described groups include a hydroxy group, a halogen atom (e.g., fluorine, chlorine, bromine or iodine), a nitro group, a cyano group, an alkyl group, an alkoxy group (e.g., methoxy, ethoxy, hydroxyethoxy, propoxy, hydroxypropoxy, n-butoxy, isobutoxy, sec-butoxy or tert-butoxy), an alkoxycarbonyl group (e.g., methoxycarbonyl or ethoxycarbonyl), an aralkyl group (e.g., benzyl phenethyl or cumyl), an aralkyloxy group, an acyl group (e.g., formyl, acetyl, butyryl, benzoyl, cinnamoyl or valeryl), an acyloxy group (e.g., butyryloxy), an alkenyl group, an alkenyloxy group (e.g., vinyloxy, propenyloxy, allyoxy or butenyloxy), an aryl group, an aryloxy group (e.g., phenyloxy) and an aryloxycarbonyl group (e.g., phenyloxycarbonyl).
R3 preferably represents an alkyl group having from 1 to 20 carbon atoms, an aryl group having from 6 to 20 carbon atoms or an aralkyl group having from 7 to 20 carbon atoms. These groups may further have a substituent.
Specific examples of the group represented by formula (X) are set forth below, but the present invention should not be construed as being limited thereto. 
Resin (A), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (X) (hereinafter also referred to as a resin having a group represented by formula (X)) is a compound that becomes alkali-soluble by the action of an acid and has a structure obtained by introducing an acid-decomposable group represented by formula (X) into a compound having a molecular weight distribution obtained by polymerization of monomer.
The resin having a group represented by formula (X) includes resins having a group represented by formula (X) in the main chain thereof, the side chain thereof or both of the main chain and side chain thereof. Of the resins, those having a group represented by formula (X) in the side chain thereof are more preferred.
A parent resin in the case wherein the group represented by formula (X) is bonded as a side chain includes an alkali-soluble resin having an xe2x80x94OH group or a xe2x80x94COOH group, preferably an xe2x80x94R0xe2x80x94COOH group or an xe2x80x94Arxe2x80x94OH group, in the side chain. In the above formulae, xe2x80x94R0xe2x80x94 represents a two or higher valent aliphatic or aromatic hydrocarbon group which may have a substituent and xe2x80x94Arxe2x80x94 represents a two or higher valent monocyclic or polycyclic aromatic group which may have a substituent.
The parent resin preferably used in the present invention includes an alkali-soluble resin having a phenolic hydroxy group.
Of the alkali-soluble resins having a phenolic hydroxy group, a copolymer containing at least 30% by mole, preferably at least 50% by mole, of a repeating unit corresponding to o-, m- or p-hydroxystyrene (collectively referred to as hydroxystyrene) or o-, m- or p-hydroxy-xcex1-methylstyrene (collectively referred to as hydroxy-xcex1-methylstyrene), a homopolymer thereof, and such a copolymer or homopolymer wherein the benzene ring in the repeating unit described above is partially hydrogenated are preferable. p-Hydroxystyrene homopolymer is more preferred.
Monomers other than the hydroxystyrene and hydroxy-xcex1-methylstyrene, which can be used for the preparation of copolymer, include preferably an acrylic ester, a methacrylic ester, an acrylamide, a methacrylamide, acrylonitrile, methacrylonitrile, maleic anhydride, styrene, xcex1-methylstyrene, acetoxystyrene and an alkoxystyrene, more preferably styrene, acetoxystyrene and tert-butoxystyrene.
A content of the repeating unit (structural unit) including a group represented by formula (X) in the resin is preferably from 5 to 50% by mole, more preferably from 5 to 30% by mole, based on the total repeating unit of the resin.
The resin including a group represented by formula (X) according to the present invention may also contain an acid-decomposable group other than the group represented by formula (X).
The resin including a group represented by formula (X) can be obtained by synthesizing a corresponding vinyl ether and reacting the vinyl ether with an alkali-soluble resin having a phenolic hydroxy group dissolved in an appropriate solvent, for example, tetrahydrofuran in a conventional manner. The reaction is carried out ordinarily in the presence of an acidic catalyst, preferably an acidic ion exchange resin, hydrochloric acid, p-toluenesulfonic acid or a salt, for example, pyridinium tosylate. The corresponding vinyl ether can be synthesized, for example, by a method using a nucleophilic substitution reaction from an active starting material, e.g., chloroethyl vinyl ether or a method using a mercury or palladium catalyst.
According to another method, the vinyl ether can also be synthesized by an acetal exchange method using a corresponding alcohol and a vinyl ether. In such a case, the reaction is conducted by mixing an alcohol having the desired substituent to be introduced and a relatively unstable vinyl ether, for example, tert-butyl vinyl ether in the presence of an acidic catalyst, for example, p-toluenesulfonic acid or pyridinium tosylate.
Specific preferred examples of the structure of the resin (A) including a group represented by formula (X) are set forth below, but the present invention should not be construed as being limited thereto. 
A weight average molecular weight (Mw, calculated in terms of standard polystyrene) of the resin (A) is ordinarily not less than 2,000, preferably from 3,000 to 200,000, and more preferably from 5,000 to 70,000. A dispesity (Mw/Mn) of the resin (A) is preferably from 1.0 to 4.0, more preferably from 1.0 to 3.5, and particularly preferably from 1.0 to 3.0. As the value of dispersity is small, heat resistance and image-forming properties (for example, pattern profile or defocus latitude) of the resist composition are improved.
(a-2) Resin (B), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Y) described above:
In formula (Y), R4 represents an alkyl group.
The alkyl group represented by R4 is preferably a straight chain or branched alkyl group having up to 4 carbon atoms, and includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups.
Specific examples of the group represented by formula (Y) are set forth below, but the present invention should not be construed as being limited thereto. 
Resin (B), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Y) (hereinafter also referred to as a resin having a group represented by formula (Y)) is a compound that becomes alkali-soluble by the action of an acid and has a structure obtained by introducing an acid-decomposable group represented by formula (Y) into a compound having a molecular weight distribution obtained by polymerization of monomer.
The resin having a group represented by formula (Y) includes resins having a group represented by formula (Y) in the main chain thereof, the side chain thereof or both of the main chain and side chain thereof. Of the resins, those having a group represented by formula (Y) in the side chain thereof are more preferred.
A parent resin in the case wherein the group represented by formula (Y) is bonded as a side chain includes an alkali-soluble resin having an xe2x80x94OH group or a xe2x80x94COOH group, preferably an xe2x80x94R0xe2x80x94COOH group or an xe2x80x94Arxe2x80x94OH group, in the side chain. In the above formulae, xe2x80x94R0xe2x80x94 represents a two or higher valent aliphatic or aromatic hydrocarbon group which may have a substituent and xe2x80x94Arxe2x80x94 represents a two or higher valent monocyclic or polycyclic aromatic group which may have a substituent.
The parent resin preferably used in the present invention includes an alkali-soluble resin having a phenolic hydroxy group.
Of the alkali-soluble resins having a phenolic hydroxy group, a copolymer containing at least 30% by mole, preferably at least 50% by mole, of a repeating unit corresponding to o-, m- or p-hydroxystyrene (collectively referred to as hydroxystyrene) or o-, m- or p-hydroxy-xcex1-methylstyrene (collectively referred to as hydroxy-xcex1-methylstyrene), a homopolymer thereof, and such a copolymer or homopolymer wherein the benzene ring in the repeating unit described above is partially hydrogenated are preferable. p-Hydroxystyrene homopolymer is more preferred.
Monomers other than the hydroxystyrene and hydroxy-xcex1-methylstyrene, which can be used for the preparation of copolymer, include preferably an acrylic ester, a methacrylic ester, an acrylamide, a methacrylamide, acrylonitrile, methacrylonitrile, maleic anhydride, styrene, xcex1-methylstyrene, acetoxystyrene and an alkoxystyrene, more preferably styrene, acetoxystyrene and tert-butoxystyrene.
A content of the repeating unit (structural unit) including a group represented by formula (Y) in the resin is preferably from 5 to 70% by mole, more preferably from 5 to 50% by mole, based on the total repeating unit of the resin.
The resin including a group represented by formula (Y) according to the present invention may also contain an acid-decomposable group other than the group represented by formula (Y).
The resin including a group represented by formula (Y) can be obtained by synthesizing a corresponding vinyl ether and reacting the vinyl ether with an alkali-soluble resin having a phenolic hydroxy group dissolved in an appropriate solvent, for example, tetrahydrofuran in a conventional manner. The reaction is carried out ordinarily in the presence of an acidic catalyst, preferably an acidic ion exchange resin, hydrochloric acid, p-toluenesulfonic acid or a salt, for example, pyridinium tosylate. The corresponding vinyl ether can be synthesized, for example, by a method using a nucleophilic substitution reaction from an active starting material, e.g., chloroethyl vinyl ether or a method using a mercury or palladium catalyst.
According to another method, the vinyl ether can also be synthesized by an acetal exchange method using a corresponding alcohol and a vinyl ether. In such a case, the reaction is conducted by mixing an alcohol having the desired substituent to be introduced and a relatively unstable vinyl ether, for example, tert-butyl vinyl ether in the presence of an acidic catalyst, for example, p-toluenesulfonic acid or pyridinium tosylate.
Specific preferred examples of the structure of the resin (B) including a group represented by formula (Y) are set forth below, but the present invention should not be construed as being limited thereto. 
A weight average molecular weight (Mw, calculated in terms of standard polystyrene) of the resin (B) is ordinarily not less than 2,000, preferably from 3,000 to 200,000, and more preferably from 5,000 to 70,000. A dispesity (Mw/Mn) of the resin (A) is preferably from 1.0 to 4.0, more preferably from 1.0 to 3.5, and particularly preferably from 1.0 to 3.0. As the value of dispersity is small, heat resistance and image-forming properties (for example, pattern profile or defocus latitude) of the resist composition are improved.
A content of the resin (A) and/or resin (B) in the positive resist composition of the present invention is preferably from 25 to 98.998% by weight, more preferably from 40 to 95% by weight, based on the total solid content of the positive resist composition.
(a-3) Resin (C), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Q) described above:
In formula (Q), R5 and R6, which may be the same or different, each represent a hydrogen atom or an alkyl group, X represents an alkylene group which may have a substituent, Y represents a divalent connecting group, Z2 represents a heterocyclic group which may have a substituent, and 1 represents 0 or 1.
The alkyl group represented by R5 or R6 in formula (Q) is preferably a straight chain or branched alkyl group having up to 4 carbon atoms, and includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl groups. R5 and R6 each more preferably represent a hydrogen atom or a methyl group.
The alkylene group represented by X in formula (Q) is preferably an alkylene group having from 1 to 20 carbon atoms, more preferably an alkylene group having from 1 to 10 carbon atoms, and includes, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene and decanylene groups. Of these groups, ethylene, propylene and butylene groups are more preferred.
The alkylene group may have a substituent, and examples of the substituent include a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a tolyl group and a cyclohexyl group.
A hetero ring included in the heterocyclic group represented by Z2 includes, for example, thiirane, thiolane, thiophene, furan, pyrrole, benzothiophene, benzofuran, benzopyrrole, triazine, imidazole, benzimidazole, triazole, thiadiazole, thiazole and pyrrolidone. However, the hetero ring should not be construed as being limited to these rings and any ring ordinarily called as a hetero ring (including a ring formed by a carbon atom and a hetero atom and a ring formed by a hetero atom) may be used.
Examples of the substituent for the heterocyclic group represented by Z2 include a hydroxy group, a halogen atom (e.g., fluorine, chlorine, bromine or iodine), a nitro group, a cyano group, an alkyl group, an alkoxy group (e.g., methoxy, ethoxy, hydroxyethoxy, propoxy, hydroxypropoxy, n-butoxy, isobutoxy, sec-butoxy or tert-butoxy), an alkoxycarbonyl group (e.g., methoxycarbonyl or ethoxycarbonyl), an aralkyl group (e.g., benzyl phenethyl or cumyl), an aralkyloxy group, an acyl group (e.g., formyl, acetyl, butyryl, benzoyl, cinnamoyl or valeryl), an acyloxy group (e.g., butyryloxy), an alkenyl group, an alkenyloxy group (e.g., vinyloxy, propenyloxy, allyoxy or butenyloxy), an aryl group, an aryloxy group (e.g., phenyloxy) and an aryloxycarbonyl group (e.g., phenyloxycarbonyl).
The divalent connecting group represented by Y includes xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94SOxe2x80x94, xe2x80x94Sexe2x80x94 and an alkylene group having from 1 to 4 carbon atoms. The divalent groups may be used individually or in combination of two or more thereof.
Preferred examples of the divalent connecting group represented by Y includes xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Sexe2x80x94 and xe2x80x94Oxe2x80x94C(xe2x95x90O)xe2x80x94CH2xe2x80x94.
Specific examples of the group represented by formula (Q) are set forth below, but the present invention should not be construed as being limited thereto. 
Resin (C), which is decomposed by the action of an acid to increase solubility in an alkali developing solution, containing a structural unit including a group represented by formula (Q) is a compound that becomes alkali-soluble by the action of an acid and has a structure obtained by introducing an acid-decomposable group represented by formula (Q) into a compound having a molecular weight distribution obtained by polymerization of monomer.
The resin (C) includes resins having a group represented by formula (Q) in the main chain thereof, the side chain thereof or both of the main chain and side chain thereof. Of the resins, those having a group represented by formula (Q) in the side chain thereof are more preferred.
A parent resin in the case wherein the group represented by formula (Q) is bonded as a side chain includes an alkali-soluble resin having an xe2x80x94OH group or a xe2x80x94COOH group, preferably an xe2x80x94R0xe2x80x94COOH group or an xe2x80x94Arxe2x80x94OH group, in the side chain. In the above formulae, xe2x80x94R0xe2x80x94 represents a two or higher valent aliphatic or aromatic hydrocarbon group which may have a substituent and xe2x80x94Arxe2x80x94 represents a two or higher valent monocyclic or polycyclic aromatic group which may have a substituent.
The parent resin preferably used in the present invention includes an alkali-soluble resin having a phenolic hydroxy group.
Of the alkali-soluble resins having a phenolic hydroxy group, a copolymer containing at least 30% by mole, preferably at least 50% by mole, of a repeating unit corresponding to o-, m- or p-hydroxystyrene (collectively referred to as hydroxystyrene) or o-, m- or p-hydroxy-xcex1-methylstyrene (collectively referred to as hydroxy-xcex1-methylstyrene), a homopolymer thereof, and such a copolymer or homopolymer wherein the benzene ring in the repeating unit described above is partially hydrogenated are preferable. p-Hydroxystyrene homopolymer is more preferred.
Monomers other than the hydroxystyrene and hydroxy-xcex1-methylstyrene, which can be used for the preparation of copolymer, include preferably an acrylic ester, a methacrylic ester, an acrylamide, a methacrylamide, acrylonitrile, methacrylonitrile, maleic anhydride, styrene, xcex1-methylstyrene, acetoxystyrene and an alkoxystyrene, more preferably styrene, acetoxystyrene and tert-butoxystyrene.
A content of the repeating unit (structural unit) including a group represented by formula (Q) in the resin is preferably from 5 to 50% by mole, more preferably from 5 to 40% by mole, based on the total repeating unit of the resin.
The resin including a group represented by formula (Q) according to the present invention, which is a polymeric dissolution inhibiting compound, may also contain an acid-decomposable group other than the group represented by formula (Q).
The resin (C) including the group represented by formula (Q) can be obtained by synthesizing a corresponding vinyl ether and reacting the vinyl ether with an alkali-soluble resin having a phenolic hydroxy group dissolved in an appropriate solvent, for example, tetrahydrofuran in a conventional manner. The reaction is carried out ordinarily in the presence of an acidic catalyst, preferably an acidic ion exchange resin, hydrochloric acid, p-toluenesulfonic acid or a salt, for example, pyridinium tosylate.
A weight average molecular weight (Mw, calculated in terms of standard polystyrene) of the resin (C) including the group represented by formula (Q) is preferably from 3,000 to 80,000, and more preferably from 7,000 to 50,000. A dispersity (Mw/Mn) of the resin (C) is ordinarily from 1.01 to 4.0, and preferably from 1.05 to 3.00. In order to obtain the polymer having such a dispersity, an anion polymerization method or a radical polymerization method is preferably employed.
Specific preferred examples of the structure of the resin (C) including a group represented by formula (Q) are set forth below, but the present invention should not be construed as being limited thereto. 
A content of the resin (C) in the positive resist composition of the present invention is preferably from 1.0 to 70% by weight, more preferably from 5.0 to 50% by weight, based on the total solid content of the positive resist composition.
(b) Compound that generates an acid upon irradiation of an actinic ray or radiation (hereinafter, also referred to as an xe2x80x9cphoto-acid generatorxe2x80x9d):
The photo-acid generator of component (b) for use in the present invention is a compound that generates an acid upon irradiation of an actinic ray or radiation.
The photo-acid generator for use in the present invention can be appropriately selected from photo-initiators for photo-cationic polymerization, photoinitiators for photo-radical polymerization, photo-achromatic agents for dyes, photo-discoloring agents, compounds generating an acid upon irradiation of known light used for a microresist (an ultraviolet ray or far ultraviolet ray of from 400 to 200 nm, particularly preferably, a g-line, h-line, i-line or KrF excimer laser beam), an ArF excimer laser beam, an electron beam, an X ray, a molecular beam or an ion beam, and mixtures thereof.
Examples of such photo-acid generators include an onium salt, for example, a diazonium salt, an ammonium salt, a phosphonium salt, an iodonium salt, a sulfonium salt, a selenonium salt or an arsonium salt, an organic halogen compound, an organic metal/organic halide compound, a photo-acid generator having an o-nitrobenzyl type protective group, a compound generating a sulfonic acid upon photolysis, which is represented by an iminosulfonate, a disulfone compound, a diazoketosulfone compound and a diazodisulfone compound.
Also, polymer compounds in which a group or compound generating an acid upon irradiation of an actinic ray or radiation is introduced into the main chain or side chain thereof may be used.
Further, compounds generating an acid with light as described, for example, in V. N. R. Pillai, Synthesis, (1), 1 (1980), A. Abad et al., Tetrahedron Lett., (47) 4555 (1971), D. H. R. Barton et al., J. Chem. Soc., (C), 329 (1970), U.S. Pat. No. 3,779,778 and European Patent 126,712 may be used.
Of the photo-acid generators, those which can be particularly effectively used in the present invention are described below.
(1) Oxazole derivative substituted with a trihalomethyl group represented by formula (PAG1) shown below or S-triazine derivative substituted with a trihalomethyl group represented by formula (PAG2) shown below: 
In formulae (PAG1) and (PAG2), R201 represents a substituted or unsubstituted aryl group or a substituted or unsubstituted alkenyl group; R202 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkyl group or xe2x80x94C(Y)3; and Y represents a chlorine atom or a bromine atom.
Specific examples of such compounds are set forth below, but the present invention should not be construed as being limited thereto. 
(2) Iodonium salt represented by formula (PAG3) shown below or sulfonium salt represented by formula (PAG4) shown below: 
In formulae (PAG3) and (PAG4), Ar1 and Ar2, which may be the same or different, each independently represent a substituted or unsubstituted aryl group.
R203, R204 and R205, which may be the same or different, each independently represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group.
Zxe2x88x92 represents a counter anion. Examples of the counter anion include BF4xe2x88x92, AsF6xe2x88x92, PF6xe2x88x92, SbF6xe2x88x92, SiF62xe2x88x92, ClO4xe2x88x92, a perfluoroalkane sulfonic acid anion, e.g., CF3SO3xe2x88x92, an alkylsulfonic acid anion, e.g., camphorsulfonic acid anion, an aromatic sulfonic anion, e.g., pentafluorobenzenesulfonic acid anion, benzenesulfonic acid anion or triisopropylbenzenesulfonic acid anion, a condensed polynuclear aromatic sulfonic anion, e.g., naphthalene-1-sulfonic acid anion, an anthraquinone sulfonic acid anion and a dye containing a sulfonic acid group, however, the present invention should not be construed as being limited thereto. The anion moiety may further has a substituent.
Two of R203, R204 and R205 or Ar1 and Ar2 may be combined with each other through a single bond or a substituent.
Specific examples of such compounds are set forth below, but the present invention should not be construed as being limited thereto. 
The onium salts represented by formulae (PAG3) and (PAG4) are known and can be synthesized by methods described, for example, in J. W. Knapczyk et al., J. Am. Chem. Soc., 91, 145 (1969), A. L. Maycok et al., J. Org. Chem., 35, 2532 (1970), E. Goethas et al., Bull. Soc. Chem. Belg., 73, 546 (1964), H. M. Leicester, J. Ame. Chem. Soc., 51, 3587 (1929), J. V. Crivello et al., J. Polym. Chem. Ed., 18, 2677 (1980), U.S. Pat. Nos. 2,807,648 and 4,247,473 and JP-A-53-101331 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d).
(3) Disulfone derivative represented by formula (PAG5) shown below or iminosulfonate derivative represented by formula (PAG6) shown below: 
In formulae (PAG5) and (PAG6), Ar3 and Ar4 which may be the same or different, each independently represent a substituted or unsubstituted aryl group; R206 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group; and A represents a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group or a substituted or unsubstituted arylene group.
Specific examples of such compounds are set forth below, but the present invention should not be construed as being limited thereto. 
(4) Diazodisulfone derivative represented by formula (PAG7) shown below: 
In formula (PAG7), R represents a straight chain, branched or cyclic alkyl group or a substituted or unsubstituted aryl group.
Specific examples of such compounds are set forth below, but the present invention should not be construed as being limited thereto. 
The compound that generates an acid upon irradiation of an actinic ray or radiation of component (b) is preferably at least one of a compound having a sulfonium salt structure and a compound having a diazosulfone structure, and more preferably a combination of the compound having a sulfonium salt structure and the compound having a diazosulfone structure, because the effects of the present invention are more remarkably achieved.
An amount of the photo-acid generator added is ordinarily from 0.001 to 40% by weight, preferably from 0.01 to 20% by weight, and more preferably from 0.1 to 5% by weight, based on the total solid content of the positive resist composition. When the amount of photo-acid generator added is less than 0.001% by weight, the photospeed may remain low. On the other hand, it is not preferred that the amount of photo-acid generator added is more than 40% by weight, because light absorption of the resist composition excessively increases to cause degradation of profile and narrowing of process margin (particularly, narrowing of bake margin).
The positive resist composition of the present invention may contain an organic basic compound. It is preferred to add the organic basic compound to the positive resist composition, because stability of the resist composition during preservation is improved and the variation of linewidth due to PED is more suppressed.
The organic basic compound preferably used in the present invention is a compound having basicity higher than phenol. Among others, nitrogen-containing basic compounds are preferred.
Preferred chemical circumstance includes a structure represented by any one of the following formulae (A) to (E): 
In the above formula, R250, R251 and R252 which may be the same or different, each represent a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, an aminoalkyl group having from 1 to 6 carbon atoms, a hydroxyalkyl group having from 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having from 6 to 20 carbon atoms, or R251 and R252 may be combined with each other to form a ring, 
In the above formulae, R253, R254, R255 and R256, which may be the same or different, each represent an alkyl group having from 1 to 6 carbon atoms.
More preferred organic basic compounds are nitrogen-containing cyclic compounds (also referred to as a cyclic amine compound) and nitrogen-containing basic compounds having two or more nitrogen atoms having different chemical circumstances per molecule.
The cyclic amine compound preferably has a polycyclic structure. Specific preferred examples of the cyclic amine compound include compounds represented by the following formula (F): 
In formula (F), Y and Z, which may be the same or different, each independently represent a straight chain, branched or cyclic alkylene group, which may contain a hetero atom or may be substituted.
Examples of the hetero atom includes a nitrogen atom, a sulfur atom and an oxygen atom. The alkylene group preferably has from 2 to 10 carbon atoms, and more preferably from 2 to 5 carbon atoms. Examples of the substituent for the alkylene group include an alkyl group having from 1 to 6 carbon atoms, an aryl group, an alkenyl group, a halogen atom and a halogen-substituted alkyl group. Specific examples of the compound represented by formula (F) are set forth below. 
Of the cyclic amine compound represented by formula (F), 1,8-diazabicyclo[5.4.0]undec-7-ene and 1,5-diazabicyclo[4.3.0]non-5-ene are particularly preferred.
Of the nitrogen-containing basic compounds having two or more nitrogen atoms of different chemical circumstances per molecule, those particularly preferred include compounds containing both a substituted or unsubstituted amino group and a cyclic structure including a nitrogen atom and compounds having an alkylamino group. Preferred specific examples thereof include substituted or unsubstituted guanidines, substituted or unsubstituted aminopyridines, substituted or unsubstituted aminoalkylpyridines, substituted or unsubstituted aminopyrrolidines, substituted or unsubstituted indazoles, substituted or unsubstituted pyrazoles, substituted or unsubstituted pyrazines, substituted or unsubstituted pyrimidines, substituted or unsubstituted purines, substituted or unsubstituted imidazolines, substituted or unsubstituted pyrazolines, substituted or unsubstituted piperazines, substituted or unsubstituted aminomorpholines and substituted or unsubstituted aminoalkylmorpholines. Preferred examples of the substituent include an amino group, an aminoalkyl group, an alkylamino group, an aminoaryl group, an arylamino group, an alkyl group, an alkoxy group, an acyl group, an acyloxy group, an aryl group, an aryloxy group, a nitro group, a hydroxy group and a cyano group.
Preferred specific examples thereof include guanidine, 1,1-dimethylguanidine, 1,1,3,3-tetramethylguanidine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-dimethylaminopyridine, 4-dimethylaminopyridine, 2-diethylaminopyridine, 2-(aminomethyl)pyridine, 2-amino-3-methylpyridine, 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-6-methylpyridine, 3-aminoethylpyridine, 4-aminoethylpyridine, 3-aminopyrrolidine, piperazine, N-(2-aminoethyl)piperazine, N-(2-aminoethyl)piperidine, 4-amino-2,2,6,6-tetramethylpiperidine, 4-piperidinopiperidine, 2-iminopiperidine, 1-(2-aminoethyl)pyrrolidine, pyrazole, 3-amino-5-methylpyrazole, 5-amino-3-methyl-1-p-tolylpyrazole, pyrazine, 2-(aminomethyl)-5-methylpyrazine, pyrimidine, 2,4-diaminopyrimidine, 4,6-dihydroxypyrimidine, 2-pyrazoline, 3-pyrazoline, N-aminomorpholine, N-(2-aminoethyl)morpholine, trimethylimidazole, triphenylimidazole and methyldiphenylimidazole. However, the nitrogen-containing basic compounds for use in the present invention should not be construed as being limited thereto.
The organic basic compounds may be used individually or as a mixture of two or more thereof. An amount of the organic basic compound used is ordinarily from 0.001 to 10 parts by weight, preferably from 0.01 to 5 parts by weight, based on 100 parts by weight of the positive resist composition (excluding a solvent) of the present invention. When the amount is less than 0.001 parts by weight, an effect of the addition of organic basic compound is not obtained. When the amount exceeds 10 parts by weight, on the other hand, the sensitivity tends to decrease or the developability tends to degrade in the unexposed area.
Into the chemically amplified positive resist composition of the present invention, other additives, for example, a surface active agent, a dye, a pigment, a plasticizer, a photosensitizer or a compound promoting dissolution in a developing solution, which has at least two phenolic hydroxy groups, may be incorporated.
The positive resist composition of the present invention preferably contains a surface active agent. Specific examples of the surface active agent include a nonionic surface active agent, for example, a polyoxyethylene alkyl ether, e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether or polyoxyethylene oleyl ether, a polyoxyethylene alkyl aryl ether, e.g., polyoxyethylene octyl phenol ether or polyoxyethylene nonyl phenol ether, a polyoxyethylene/polyoxypropylene block copolymer, a sorbitan fatty acid ester, e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate or sorbitan tristearate, or a polyoxyethylene sorbitan fatty acid ester, e.g., polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate or polyoxyethylene sorbitan tristearate, a fluorine-based surface active agent, for example, Eftop EF301, EF303 and EF352 (manufactured by Shin-Akita Kasei Co., Ltd.), Megafac F171, F173, F176, F189 and R08 (manufactured by Dainippon Ink and Chemicals, Inc.), Fluorad FC430 and FC431 (manufactured by Sumitomo 3M Ltd.) or Asahiguard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105 and SC106 (manufactured by Asahi Glass Co., Ltd.), an organosiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.), an acrylic acid or methacrylic acid (co)polymer (Polyflow No. 75 and No. 95 (manufactured by Kyoeisha Chemical Co., Ltd.) and Troysol S-366 (manufactured by Troy Chemical Corp.).
Of the surface active agents, a fluorine-based or silicon-based surface active agent is preferably used in view of good coating ability and reduced development defect.
An amount of the surface active agent added is ordinarily from 0.01 to 2% by weight, preferably from 0.01 to 1% by weight, based on the total solid content of the positive resist composition of the present invention. The surface active agents may be used individually or in combination of two or more thereof.
It is possible for the chemically amplified positive resist composition of the present invention to have sensitivity to an i-line or g-line by adding a spectral sensitizer shown below thereto so as to be sensitized in a wavelength region longer than far ultraviolet, in which the photo-acid generator used does not have absorption. Preferred examples of the spectral sensitizer include specifically benzophenone, p,pxe2x80x2-tetramethyldiaminobenzophenone, p,pxe2x80x2-tetraethyldiaminobenzophenone, 2-chlorothioxanthone, anthrone, 9-ethoxyanthracene, anthracene, pyrene, perylene, phenothiazine, benzil, Acridine Orange, Benzoflavin, Setoflavin T, 9,10-diphenylanthracene, 9-fluorenone, acetophenone, phenanthrene, 2-nitrofluorene, 5-nitroacenaphthene, benzoquinone, 2-chloro-4-nitroaniline, N-acetyl-p-nitroaniline, p-nitroaniline, N-acetyl-4-nitro-1-naphthylamine, picramide, anthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1,2-benzanthraquinone, 3-methyl-1,3-diaza-1,9-benzanthrone, dibenzalacetone 1,2-naphthoquinone, 3,3xe2x80x2-carbonylbis(5,7-dimethoxycarbonylcoumarin) and coronene. However, the spectral sensitizer used in the present invention should not be construed as being limited thereto.
The compound promoting dissolution in a developing solution, which has at least two phenolic hydroxy groups, include a polyhydroxy compound. Preferred examples of the polyhydroxy compound include a phenol, resorcin, phloroglucine, phloroglucide, 2,3,4-trihydroxybenzophenone, 2,3,4,4xe2x80x2-tetrahydroxybenzophenone, xcex1-,xcex1xe2x80x2-,xcex1xe2x80x3-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, tris(4-hydroxyphenyl)methane, tris(4-hydroxyphenyl)ethane and 1,1xe2x80x2-bis(4-hydroxyphenyl)cyclohexane.
The chemically amplified positive resist composition of the present invention is used by dissolving the above-described components in a solvent, which can dissolve the components, and coating the resulting solution on a substrate. Preferred examples of the solvent used include ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, xcex3-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methylpyruvate, ethyl pyruvate, propyl pyruvate, N,N-dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone and tetrahydrofuran. The solvents may be used individually or as a mixture of two or more thereof.
The chemically amplified positive resist composition is applied to a substrate (e.g., silicon/silicon dioxide coating) as used for the production of a precision integrated circuit element by means of an appropriate coating method, for example, using a spinner or coater. After the application, the resulting photoresist layer is exposed to light through the desired mask, followed by baking and development. Thus, good resist patterns are obtained.
The developing solution for the chemically amplified positive resist composition of the present invention includes an aqueous solution containing, alkali, for example, an inorganic alkali, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium phosphate, sodium metasilicate or aqueous ammonia, a primary amine, e.g., ethylamine or n-propylamine, a secondary amine, e.g., diethylamine or di-n-butylamine, a tertiary amine, e.g., triethylamine or methyldiethylamine, an alcohol amine, e.g., dimethylethanolamine or triethanolamine, an amide, e.g., formamide or acetamide, a quaternary ammonium salt, e.g., tetramethylammonium hydroxide, trimethyl(2-hydroxyethyl)ammonium hydroxide, tetraethylammonium hydroxide, tributylmethylammonium hydroxide, tetraethanolammonium hydroxide, methyltriethanolammonium hydroxide, benzylmethyldiethanolammonium hydroxide, benzyldimethylethanolammonium hydroxide, benzyltriethanolammonium hydroxide, tetrapropylammonium hydroxide or tetrabutylammonium hydroxide, and a cyclic amine, e.g., pyrrole or piperidine.
The present invention is described in more detail with reference to the following examples, but the present invention should not be construed as being limited thereto.